Apparatus for forge-forming outer-ring of constant velocity joint and method thereof

ABSTRACT

An outer-ring of a constant velocity joint is fabricated by pressing an inner surface of the pre-processed outer-ring (2A) set in a lower die (3) by using a forging punch (20) in which plural punch pieces (11) each having a protrusion (111) corresponding to the ball track groove (6) are slidably coupled to plural downwardly tapered grooves (131) of a punch piece slide member (13), so that an upper periphery (9A) of the pre-processed outer-ring (2A) is contracted in line with a head shape of the forging punch (20), and ascending the forging punch.

TECHNICAL FIELD

The present invention relates in general to an apparatus and method forforge-forming an outer-ring of a constant velocity joint, and moreparticularly to an apparatus for forge-forming the outer-ring ofconstant velocity joint capable of producing a high precision outer-ringby only a contraction of punch pieces instead of expansion andcontraction, and of preventing breakage of the punch pieces bysimplifying the structure of an outer-ring forging punch and a lowerpress, and a method thereof.

BACKGROUND ART

The constant velocity joint has dual shafts in which and inner-ring 1and outer-ring 2 formed at its end are connected through a torquetransmitting ball 3 inserted into ball grooves 5 and 6 which are formeduniformly between the inner-ring and outer-ring as shown in FIGS. 1 and2.

A peripheral surface 7 of the inner-ring 1, an inner surface 8 of theouter-ring 2, and a ball cage 4 are formed of a spherical surface inwhich its center of curvature is located at the center of joint 0, andthe ball groove 5 of the inner-ring 1 and the ball grove 6 of theouter-ring 2 are formed of curves which have the center of curvature onoffset points A and B aparted equal distance from the center of joint 0.Therefore, since a track of ball center travelling the ball groove hasthe curve with the center of curvature at points A and B, the ball 3 isalways directed to a plane bisecting an angle which dual shafts form,thereby maintaining the constant velocity.

To fabricate such an outer-ring of the constant velocity joint in whichhas the inner surface of the spherical surface and the ball groove ofthe curved surface, the prior art method forms the inner surface and theball groove by cut-forming an outer-ring forming material in which boththe inner surface and the ball groove are hot forged as straight.

However, since the centers of curvature of the spherical inner surface 8and the ball groove 6 are equal each other and there shapes arecomplicated, it takes long time in fabricating it by milling and wastesmany portions of the forming material.

Recently, many fabricating apparatuses for the constant velocity jointhave been developed and used. For example, Japanese Laid-open PatentGazette No. 57-177843 discloses a method of fabricating the outer-ringof the constant velocity joint. This method prepares a pre-formedmaterial in which the inner surface is formed as conical shape whichexpands from maximum diameter portion to apature end, the ball groovesare formed on the inner surface as straight from maximum diameterportion to apature end, and small escaping grooves are formed on thespherical surface between ball grooves.

Then, the inner surface of the material is contracted from the peripheryto diameter direction on a die having a conical inner surface, by usingseperate type punch which plural curve forming members are mountedcontractably and a protruding punch, in the state that gap between curveforming members are located in line with the escaping grooves of thematerial.

The above-mentioned technique has problems which are apt to break punchpieces and a punch piece guiding shaft due to vertical load in massproduction and are difficult to replace the broken punch pieces for newpunch pieces. Further, since the punch pieces are coupled to the punchpiece guiding shaft with gap, undersirable protrusion portions areformed in the spherical inner surface of the inner-ring after forgeforming.

Since the punch pieces may be shifted right and left, the precise bisectangle of ball track grooves and the distance therebetween can not beguaranteed in the formed outer-ring.

To solve such problems of the above technique, another outer-ringforging apparatus and method have been proposed at Korean Patent GazetteNo. 91-3896. This technique forms spherical inner suface and ball trackgrooves by forging a material in which semicircled track grooves andcircular surface are formed previously.

However, according to this technique, the outer-ring is fabricated bypressing, expansion and contraction of punch pieces.

Thus, the punch for executing the expansion and contraction of the punchpieces has the structure which does not guarantee the durability in massproduction as follows: the structure of a supporting ring nut to couplebetween the punch holder and punch pieces, elastical ring forcontraction of the punch pieces, and expanding structure of punch piecesby a mandrel. In addition, since die hole of the lower die is used asdrop passage of the formed outer-ring, the lower die does not functionas sufficient support when forge forming the outer-ring.

DISCLOSURE OF INVENTION

It is an object of the invention to provide a forge-forming apparatuscapable of producing a high precision outer-ring of constant velocityjoint and preventing breakage of the punch pieces by simplifying astructure of an outer-ring forging punch and a lower die andguaranteeing smooth forming operation of the punch piece assembly.

It is an another object of the invention to provide a forge-formingmethod capable of producing a high precision outer-ring by pressing andcontraction of punch pieces.

According to a first feature of the present invention, there is providedan outer-ring forge-forming apparatus of a constant velocity jointhaving a spherical inner surface and a plurality of curved ball trackgrooves comprising:

a plurality of punch pieces, each having a protrusion which is, at thelower portion, formed of a hemisphere shape corresponding to the curvedball track groove, and an angled protrusion at its upper end;

a punch piece slide member having a plurality of downwardly taperedgrooves in which said plurality of punch pieces are coupled slidably;

an outer tube having, at its lower end, an inwardly extending portionwhich supports said punch piece slide member and forms a sliding guidein cooperation with said tapered grooves of the punch piece slidemember;

a plurality of resilient member assemblies formed in the inwardlyextending portion for supporting resiliently said plurality of punchpieces; and

a lower die having an inner surface of the same shape as an exteriorsurface of the outer-ring.

According to a second feature of the invention, there is provided anouter-ring forging punch of a constant velocity joint comprising:

a plurality of punch pieces, each having a hemispher-shape protrusion atthe lower portion and an inward protrusion at the upper portion;

a punch piece slide member having a plurality of downwardly taperedgrooves, said each tapered groove having a deep groove corresponding tothe inward protrusion;

a plurality of resilient member, each inserted between the deep grooveand the inward protrusion for urging the punch pieces in the upwarddirection;

a stem coupled to a through-hole of the slide member and having aspherical protrusion at its lower end; and

an outer tube for accomodating and supporting the slide member in whichthe punch pieces and the stem are coupled and guiding sliding of thepunch pieces in an up and down movement.

According to a third feature of the invention, there is provided anouter-ring forging punch of a constant velocity joint comprising:

a plurality of punch pieces, each having a protrusion which is, at thelower portion, formed of a hemispher shape corresponding to a ball trackgroove the outer-ring and an angled protrusion at its upper end;

a punch piece slide member having a plurality of downwardly taperedgrooves in which said plurality of punch pieces are coupled slidably;

a stem coupled to a central through-hole of the slide member and havinga spherical protrusion at its lower end;

an outer tube for accomodating and supporting the slide member in whichthe punch pieces 16 and the stem are coupled, and guiding the punchpieces in cooperation with the slide member; and

means inserted between the angled protrusion of the punch pieces and theouter tube for returning the puch pieces.

According to a fourth feature of the invention, there is provided amethod for forge-forming an outer-ring of a constant velocity jointhaving a spherical inner surface and a plurality of curved ball trackgrooves, comprising the steps of:

preparing a pre-processed outer-ring in which its spherical innersurface and curved ball track grooves expand as straight from a maximumdiameter portion to an apature end;

setting the pre-processed outer-ring in a groove of a lower die;

pressing an inner surface of the pre-processed outer-ring by using aforging punch in which a plurality of punch pieces each having aprotrusion corresponding to the ball track groove are slidably coupledto a plurality of downwardly tapered grooves of a punch piece slidemember, so that an upper periphery of the pre-processed outer-ring iscontracted in line with a head shape of the forging punch;

vertically ascending the forging punch so that said plurality of punchpieces slides along the tapered grooves of the slide member until thelower portions of the punch pieces are separated from the inner surfaceof the forged outer-ring; and

returning said plurality of punch pieces separated from the forgedouter-ring by means of a restorating force of a plurality ofcorresponding resilient member in accordance with further ascent of theforging punch.

The forge-forming punch further comprises a stem which has a sphericalprotrusion and is coupled to a through-hole formed at the center of theslide member.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a longitudinal and sectional side view of a constant velocityjoint to which the present invention is applied.

FIG. 2 is a cross-sectional front view in the center of the constantvelocity joint as shown in FIG. 1.

FIG. 3 is a cross-sectional view explaining an operation offorge-forming an outer-ring of the constant velocity joint using anouter-ring forging punch in accordance with a first embodiment of theinvention.

FIG. 4 is an enlarged cross-sectional view showing a sliding operationof the punch piece when an upper press moves up.

FIGS. 5(A) and 5(B) are longitudinal sectional view and bottom view of apunch piece slide member of the invention.

FIGS. 6(A) and 6(B) are longitudinal sectional view and bottom view of apunch piece of the invention.

FIGS. 7(A) and 7(B) are cross-sectional views of unfinished outer-ringand finished outer-ring using an outer-ring forging punch in accordancewith the first embodiment.

FIG. 8 is a cross-sectional view of a head portion of the outer-ringforging punch in accordance with the first embodiment.

FIG. 9 is a longitudinal sectional view of an outer-ring forging punchin accordance with a second embodiment of the invention.

FIG. 10 is a side view of a punch piece slide member shown in FIG. 9.

FIG. 11 is a plane view of FIG. 10.

FIG. 12 is a cross-sectional view explaining an operation offorge-forming the outer-ring using an outer-ring forging punch inaccordance with the second embodiment.

FIG. 13 is a front view of an outer-ring forging punch in accordancewith a third embodiment of the invention.

FIG. 14 is a cross-sectional view on the line A--A of FIG. 13.

FIG. 15 is a front view of a punch piece slide member shown in FIG. 14.

FIG. 16 is a plane view of FIG. 15.

FIG. 17 is a bottom view of FIG. 15.

FIG. 18 is a cross-sectional view partially showing a press apparatususing an outer-ring forging punch of the third embodiment.

FIG. 19 is a cross-sectional view of a head portion of the outer-ringforging punch as shown in FIGS. 9 and 13.

FIG. 20 is a cross-sectional view of a head portion of a punch pieceassembly in accordance with another embodiment.

FIGS. 21(A) and (B) are a longitudinal sectional view and a bottom viewof a punch piece slide member in accordance with the invention.

FIGS. 22(A) and (B) are a side view and a bottom view of a punch piececoupled to the slide member of FIG. 21.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIGS. 3 to 6, there is shown an outer-ring forging punch 20according to a first embodiment of the present invention. In thisembodiment, a reference numeral 11 designates six punch pieces, eachhaving a protrusion 111 which is located at the lower portion and isformed of a hemisphere shape corresponding to the curved ball trackgroove 6 of the outer-ring 2, and an angled protrusion 113 at its upperend. A numeral 13 designates a punch piece slide member having sixdownwardly tapered grooves 131 in which six punch pieces 11 are coupledslidably and a numeral 15 designates a stem 15 which is inserted into athrough-hole 133 formed in the center of the punch piece slide member13, the stem having a spherical protrusion 151 at its lower end. Anumeral 17 designates an outer tube having an inwardly extending portion171 at the lower end, so that the upper portion of the punch piece slidemember 13 is accommodated inside and the lower portion of the punchpiece slide member 13 is protruded outside and a numeral 19 designatessix resilient member assemblies formed in the inwardly extending portion171 of the outer tube 17.

The outer-ring forging punch 20 is fixed to a hard plate 21 by acoupling nut 25 which is coupled to an outwardly protruding portion ofthe outer tube 17 and is screw-coupled to a screw thread of a plateholder 23 in the state that a top surface of the outer-ring forgingpunch 20 is contacted with a bottom surface of the hard plate 21.

A lower press 30 is provided with a lower die 31, an inner surface 311of which has the same shape with the exterior surface of the outer-ring2. The lower die 31 is fixed by a lower die holder 33 and a coupling nut35. In a center hole of the lower die 31, an ejecting pin 37 forejecting the formed outer-ring 2 outside is coupled vertically movably.

Referring to FIGS. 5A and 5B, the punch piece slide member 13 has sixgrooves 131, each of which is downwardly tapered and is located withequivalent space each other. In addition, the lower portion of the slidemember 13 is formed of a circular bar shape having the same diameter Dalong a predetermined length, and the upper portion of the slide member13 is formed of a truncated cone shape having an upwardly increasingdiameter via a step portion 139.

Referring to FIG. 4, a front end surface 173 of the inwardly extendingportion 171 is slanted equally to a slant of the tapered grooves 131 andan exterior surface 135 of the punch piece slide member 13.

The six resilient member assemblies 19 are formed in the inwardlyextending portion 171 of the outer tube 17 corresponding to each of thesix punch pieces 11.

Each of the six resilient member assemblies 19 comprises a bolt 191which is screw-coupled to the through-hole formed in the inwardlyextending portion 171, a housing 193 which may be inserted into thethrough-hole, and a resilient spring 195 inserted into the housing 193.On the housing 193, there is provided a supporting portion 197 which ismade of copper and has a slant equal to that of bottom surface 115 ofthe angled protrusion 113 of the punch piece 11.

The operation of the outer-ring forging punch will be described withreference to FIG. 3 as follows.

As shown in FIG. 7(A), there is prepared a pre-processed outer-ring 2Ain which its spherical inner surface 5A and curved ball track grooves 6Aexpand as straight from maximum diameter portion to apature end bypre-process step.

Then, in the state that the pre-processed outer-ring 2A is set in agroove 313 of the lower die 31 as shown in left bottom of FIG. 3, theupper press 10 moves down vertically.

In accordance with a downward movement of the upper press 10, the lowerhead of the outer-ring forging punch 20 pushes the pre-processedouter-ring 2A down into the groove 313 of the lower die 31 so that theupper periphery 9A of the outer-ring 2A is contracted to enclose thehead of the outer-ring forging punch 20.

Subsequently, the outer-ring forging punch 20 moves down up to aposition shown in right of FIG. 3, the bottom of the pre-processedouter-ring 2A is pressed and thus, the periphery 9A of the outer-ring 2Aencloses the punch pieces 11 and the punch piece slide member 13, sothat the peripheral surface 9 of the outer-ring 2A is forged as a shapeequal to that of the inner surface 311 of the lower die 31 and the innersurface 5 of the outer-ring 2A is forged as a shape equal to that of thehead of the outer-ring forging punch 20. Namely, the inner surface 5 ofthe forged outer-ring 2 is formed of the spherical shape correspondingto the head of assembly of the punch piece slide member 13 and the punchpieces 11 and further, in the inner surface 5, the ball track grooves 3corresponding to the protrusions 111 of the punch pieces 11 are formedwith equal space.

After completion of forge-forming by pressing, the upper press 10ascends vertically. In this case, as shown in FIG. 4, the outer tube 17and the punch piece slide member 13 of the outer-ring forging punch 20ascend according to the ascent of the upper press 10, but six punchpieces 11 maintain the state of engaging with the upper periphery 9 ofthe forged outer-ring 2.

According to further ascent of the outer-ring forging punch 20, theresilient springs 195 within the outer tube 17 are compressed and at thesame time, the upper portions of the punch pieces slides along thetapered grooves 131 of the punch piece slide member 13. Therefore, theupper portions of the punch pieces 11 are gathered closely each otherand the lower ends of the punch pieces 11 are also gathered toward aspace which is formed according to the ascent of the slide member 13.

Accordingly, when the outer diameter of the protrusions 11 of the punchpieces is smaller than that of the apature of outer-ring 2, the punchpieces 11 are separated from the outer-ring 2 and at the same time,returns to an original position of the outer tube 17 by means of arestoring force of the compressed resilient springs 195. Then, theejecting pin 37 ascends and pushes up the finished outer-ring 2 outsideof the lower die 31.

According to the embodiment described above, after the forge-forming iscompleted by pressing step of only the outer-ring forging punch 20, theouter-ring forging punch 20 slips out of the inner periphery of thefinished outer-ring 2 by contraction and restoration action. Therefore,it is possible to simplify a structure of the outer-ring forging punch20 and the lower die 31.

According to this embodiment, since resilient member assemblies 19 aremounted at the inwardly extending portion 171 of the outer tube 17, itenables the outer-ring forging punch 20 to be constructed simply andshortly, so that it is possible to shorten the length of the punchpieces 11, thereby to improve the durability of the general outer-ringforging punch 20.

Further, the inwardly extending portion 171 of the outer tube 17functions as sliding guide of the punch pieces 11 in cooperation withthe punch piece slide member 13, so that roaming of the punch pieces 11is prevented during the sliding of the punch pieces.

In addition, since the head portion of the outer-ring forging punch 20has no gap between the punch piece slide member 13 and the punch pieces11 as shown in FIG. 8, the outer-ring forging punch has an effectivestructure in transferring the vertical force, thereby to apply biggerpressing force as compared with the prior art forge-forming punch.Therefore, reliability with respect to contraction and restoration ofthe punch pieces is improved, so it is possible to obtain the finishedouter-ring in which the inner surface and the ball track grooves areformed very precisely.

FIGS. 9 to 12 show an outer-ring forging punch in accordance with asecond embodiment of the invention. FIG. 9 is a longitudinal sectionalview of the outer-ring forging punch, FIG. 10 is a side view of a punchpiece slide merber and FIG. 11 is a plane view of FIG. 10.

Referring to FIG. 9, the forge-forming punch 20A comprises a stem 18having a spherical protrusion at a lower end, six punch pieces 16 eachhaving a protrusion 163 corresponding to a ball track groove 3 of theouter-ring 2, a punch piece slide member 14 in which the punch pieces 16are slidably coupled to grooves 141, and an outer tbe 12 surrounding theabove parts.

In an upper portion of the groove 141 of the punch piece slide member 14is formed a deep groove 141-1 in which a resilient spring 162 may beaccomodated and in an inward and upper portion of the punch piece 16, aprotruding jaw 16-1 for supporting the spring is formed. The spring 162is inserted between the groove 141-1 and protruding jaw 16-1, the punchpiece 16 is always located at the upper side of the punch piece slidemember 14. The above outer-ring forging punch 20A is mounted to an upperpress to forge-form the outer-ring as shown in FIG. 12.

The operation of forge-forming the outer-ring will now be described withreference to FIG. 12.

The operation of forge-forming the outer ring by means of the secondembodiment is substantially the same as that by means of the above firstembodiment.

Namely, in the state that the pre-processed outer-ring 2A is set in agroove of the lower die 31, the upper press moves down vertically.

In accordance with a downward movement of the upper press, the lowerhead of the outer-ring forging punch 20A pushes the pre-processedouter-ring 2A down into the groove of the lower die 31 so that the upperperiphery 9A of the outer-ring 2A is contracted to enclose the head ofthe outer-ring forging punch 20A.

Subsequently, the outer-ring forging punch 20A moves down up to aposition shown in right of FIG. 12, the bottom of the pre-processedouter-ring 2A is pressed and thus, the periphery 9A of the outer-ring 2Aencloses the punch pieces 16 and the punch piece slide member 14, sothat peripheral surface 9 of the outer-ring 2A is forged as a shapeequal to that of the inner surface of the lower die 31 and the innersurface 5A of the outer-ring 2A is forged as a shape equal to that ofthe head of the outer-ring forging punch 20A. Namely, the inner surface5 of the forged outer-ring 2 is formed of the spherical shapecorresponding to the head of assembly of the punch piece slide member 14and the punch pieces 16 and further, in the inner surface 5, the balltrack grooves 3 corresponding to the protrusions 163 of the punch pieces16 are formed with equal spaces.

After completion of forge-forming by pressing, the upper press ascendsvertically. In this case, the outer tube 12 and punch piece slide member14 of the outer-ring forging punch 20A ascend according to the ascent ofthe upper press, but six punch pieces 16 maintain the state of engagingwith the upper periphery 9 of the forged outer-ring 2.

According to further ascent of the outer-ring forging punch 20A, theresilient springs 162 within the outer tube 12 are compressed and at thesame time, the upper portions of the punch pieces slide along thetapered grooves 141 of the punch piece slide member 14. Therefore, theupper portions of the punch pieces 16 are gathered closely to each otherand the lower end of the punch pieces 16 are also gathered toward aspace which is formed according to the ascent of the slide member 14.

Accodingly, when the outer diameter of the protrusions 163 of the punchpieces 16 is smaller than that of the apature of outer-ring 2, the punchpieces 16 are separated from the outer-ring 2 and at the same time,returns to an original position of the outer tube 12 by means of arestoring force of the compressed resilient springs 162. Then, theejecting pin 37 ascends and pushes up the finished outer-ring 2 outsideof the lower die 31.

According to the second embodiment described above, after theforge-forming is completed by pressing step of only the outer-ringforging punch 20A, the outer-ring forging punch 20A slips out of theinner periphery of the finished outer-ring 2 by contraction andrestoration action. Therefore, it is possible to simplify a structure ofthe outer-ring forging punch 20A and the lower die 31.

According to this embodiment, since resilient springs 162 are insertedbetween the grooves 141-1 and protruding jaws 16-1, it enables theouter-ring forging punch 20A to be constructed simply and shortly, sothat it is possible to shorten the length of the punch pieces 16,thereby to improve the durability of the general outer-ring forgingpunch 20A.

Further, the inner tapered portion of the outer tube 12 functions assliding guide of the punch piece 16 in cooperation with the punch pieceslide member 14, so that roaming of the punch pieces 16 is preventedduring the sliding of the punch pieces.

In addition, since the head portion of the outer-ring forging punch 20Ahas no gap between the punch piece slide member 14 and the punch pieces16 as shown in FIG. 19, the outer-ring forging punch has an effectivestructure in transferring the vertical force, thereby to apply biggerpressing force as compared with the prior art forge-forming punch.Therefore, reliability with respect to contraction and restoration ofthe punch pieces is improved, so it is possible to obtain the finishedouter-ring in which the inner surface and the ball track grooves areformed very precisely.

FIGS. 13 to 19 show an outer-ring forging punch in accordance with athird embodiment of the invention.

FIG. 13 shown a front view of an outer-ring forging punch in accordancewith a third embodiment and FIG. 14 shows a cross-sectional view on theline A--A of FIG. 13.

Refering to FIGS. 13 and 14, the outer-ring forging punch 20B comprisesa stem 18 having a spherical protrusion 182 at its lower end, six punchpieces 16 each having a protrusion 163 corresponding to a ball trackgroove 3 of the outer-ring 2, a punch piece slide member 14 in which thepunch pieces 16 are slidably coupled to grooves 141 as shown in FIGS. 15to 17, and an outer tube 12 surrounding the above parts.

The stem 18 is coupled to the through-hole 183 at the center of thepunch piece slide member 14. The spherical protrusion 182 of the stem 18is limited by a large circular flange 181 integrally formed at the upperend (Refer to FIG. 14).

Each of the punch pieces 16 has an angled protrusion 164 at its upperend and the protrusion 163 which is, at the lower end, formed of a shapecorresponding to the ball track groove of the outer-ring 2.

The engled protrusion 164 has a hole 165 to which a supporting 161 isfixed. Between the supporting rod 161 and an inwardly extending portion127 of the outer tube 12, a resilient spring 162 is inserted.

On the punch piece slide member 14, the stem 18 and the punch piece 16,a punch plate 17 is disposed. Therefore, the punch piece 16 does notmove upwardly but move downwardly.

If the punch piece 16 moves down, the punch piece 16 compresses thespring 162. Thus, at the time of retraction, the punch piece 16 returnsto the original position by means of a restorating force of thecompressed spring 162.

The punch piece slide member 14 has six downwardly tapered grooves 141and a profile of reverse cone shape of the small and big diameters.

An interior of the outer tube 12 is tapered, and its exterior has a stepportion 121 to which a coupling nut 25 is coupled. Further, between theinterior of the outer tube 12 and tapered grooves 14, the uniform spacesare mintained and also functions as sliding guide of the punch pieces16.

The operation of the third embodiment is substantially the same as thatof the first and second embodiments, and thus its explanation ofoperation is omitted.

According to the third embodiment, since the respective punch pieces 16are supported by the respective springs 162, roaming of the punch piecesis prevented. Therfore, it is possible to produce the high preciseouter-ring and prevent the damage of the punch pieces.

FIG. 20 shows a head of another embodiment of an outer-ring forgingpunch. Six punch pieces 160 are generally formed of spherical shape incooperation with a slide member 140. The punch piece, further, has aprotrusion 164 which is formed of a hemisphere shape corresponding tothe ball trach groove 6.

The above-mentioned embodiments exemplify the cases that the stem iscoupled to the central through-hole of the punch piece slide member, butthis invention is not limited to this examples.

A punch piece slide member 13A may not include a stem as shown in FIGS.21(A) and (B). Instead, a small hemisphere is integrally formed to thelower portion 151A of the slide member 13A. Further, sliding grooves131A of the slide member 13A is formed of a substantially reversetriangle shape instead of rectangular shape (FIG. 19), reverse laddershape (FIG. 20), and approximately reverse triangle shape (FIG. 8). Inthis case, it is possible to receive bigger force than those of theabove cases.

FIGS. 22(A) and (B) show a side view and a bottom view of the punchpiece 11A coupled to the slide member 13A of FIG. 21, respectively.

Since such an assembly of the punch pieces 11A and the slide member 13Aincreases coupling force each other, damage of the punch pieces 11A isprevented and bigger force can be transferred.

In the above embodiments, the forging punch is mounted to the upperpress, but reversely, the forging punch may be mounted to the lower die.

From the foreging description of the structure of this inventiog it willalso be apparent to those skilled in the art that various changes otherthan those already described may be made in the size, shape, type,number and arrangement of parts described hereinbefore without theappended claims.

Industrial Appicability

The invention is applicable in forge-forming an outer-ring of a constantvelocity joint.

I claim:
 1. An outer-ring forge-forming apparatus of a constant velocityjoint having a spherical inner surface 5 and a plurality of curved balltrack grooves 6 comprising:a plurality of punch pieces 11, each having aprotrusion 111 which is, at the lower portion, formed of a hemisphereshape corresponding to the curved ball track groove 6, and an angledprotrusion 113 at its upper end; a punch piece slide member 13 having aplurality of downwardly tapered grooves 131 in which said plurality ofpunch pieces 11 are coupled slidably, and an exterior surface 135; anouter tube 17 having, at its lower end, an inwardly extending portion171 which supports said punch piece slide member 13 and forms a slidingguide in cooperation with said tapered grooves 131 of the punch pieceslide member 13, said inwardly extending portion 171 having a front endsurface 173 slanted equally to a slant of the tapered grooves 131 andsaid exterior surface 135 of the punch piece slide member 13; aplurality of resilient member assemblies 19 formed in the inwardlyextending portion 171 for supporting resiliently said plurality of punchpieces 11; a lower die 31 having an inner surface of the same shape asan exterior surface 9 of the outer-ring wherein a lower portion of theslide member 13 has a circular bar shape with a constant diameter alonga predetermined length and an upper portion of the slide member 13 has atruncated cone shape with an upwardly increasing diameter via a stepportion 139; an assembly of the slide member 13 and punch pieces 11 hasno gap between the slide member 13 and the punch pieces
 11. 2. Anouter-ring forge-forming apparatus according to claim 1, wherein saideach of plurality of resilient member assemblies comprises;a bolt 191which is screw-coupled to a through-hole formed in the inwardlyextending portion 171; a housing 193 which can be inserted into thethrough-hole; and a resilient spring 195 inserted into the housing 193.3. An outer-ring forge-forming apparatus according to claim 1, whereinsaid each tapered groove 131 is formed of reverse triangle shape, and across section of said each punch piece 11 is formed of reverse triangleshape correspon- ding to said tapered groove
 131. 4. An outer-ringforging punch of a constant velocity joint comprising:a plurality ofpunch pieces 16, each having a hemisphere-shape protrusion 163 at thelower portion and an inward protrusion 16-1 at the upper portion; apunch piece slide member 14 having a plurality of downwardly taperedgrooves 141, said each tapered groove 141 having a deep groove 141-1corresponding to the inward protrusion 16-1; a plurality of resilientmember 162, each inserted between the deep groove 141-1 and the inwardprotrusion 16-1 for urging the punch pieces 16 in the upward direction;a stem 18 coupled to a through-hole of the slide member 14 and having aspherical protrusion at it slower end; and an outer tube 12 foraccommodating and supporting the slide member 14 in which the punchpieces 16 and the stem 18 are coupled and guiding sliding of the punchpieces 16 in an up and down movement; a punch piece slide member 14having a plurality of downwardly tapered grooves 141 in which aplurality of punch pieces 16, 160 are coupled slidably; wherein saideach groove 141 of the slide member 14 has a rectangular-shape; threesurfaces of each punch piece 160 are buried in each groove 141 and aprotrusion 163 of each punch piece is exposed; and said each groove 141of the slide member 14 is formed of reverse ladder-shape, three surfacesof each punch piece 160 are buried in each groove, an outer surface ofeach punch piece 160 is formed of spherical shape together with an outersurface of the slide member 140, and the protrusion 163 is disposed inthe center of the outer surface of each punch piece
 160. 5. Anouter-ring forging punch of a constant velocity joint comprising:aplurality of punch pieces 16, 160 each having a protrusion 163 which is,at the lower portion, formed of a hemisphere shape corresponding to aball track groove 6 of the outer-ring and an angled protrusion 164 atits upper end; a punch piece slide member 14 having a plurality ofdownwardly tapered grooves 141 in which a plurality of punch pieces 16,160 are coupled slidably; a stem 18 coupled to a central through-hole183 of the slide member 14 and having a spherical protrusion 182 at itslower end; an outer tube 12 for accommodating and supporting the slidemember 14 in which the punch pieces 16 and the stem 18 are coupled, andguiding the punch pieces in cooperation with the slide member 14; andmeans 162 inserted between the angled protrusion 162 of the punch piecesand the outer tube 12 for returning the punch pieces; wherein said eachgroove 141 of the slide member 14 has a rectangular-shape; threesurfaces of each punch piece 16 are buried in each groove 141 and thehemisphere surface 163 of the punch piece is exposed; and said eachgroove 141 of the slide member 14 is formed of reverse ladder-shape,three surfaces of each punch piece 160 are buried in each groove, anouter surface of each punch piece 160 is formed of spherical shapetogether with an outer surface of the slide member 140, and theprotrusion 163 is disposed in the center of the outer surface of eachpunch piece
 160. 6. A method for forge-forming an outer-ring of aconstant velocity joint having a spherical inner surface 5 and aplurality of curved ball track grooves 6, comprising the stepsof:preparing a pre-processed outer-ring 2A in which its spherical innersurface 5A and curved ball track grooves 6A expand as straight from amaximum diameter portion to an apature end; setting the pre-processedouter-ring 2A in a groove 313 of a lower die 31; pressing an innersurface of the pre-processed outer-ring 2A by using a forging punch 20in which a plurality of punch pieces 11 each having a protrusion 111corresponding to the ball track groove 6 are slidably coupled to aplurality of downwardly tapered grooves 131 of a punch piece slidemember 13, so that an upper periphery 9A of the pre-processed outer-ring2A is contracted in line with a head shape of the forging punch 20;vertically ascending the forging punch 20 so that said plurality ofpunch pieces 1 slides along the tapered grooves 131 of the slide member13 until the lower portions of the punch pieces are separated from theinner surface of the forged outer-ring 2; and returning said pluralityof punch pieces 11 separated from the forged outer-ring by means of arestorating force of a plurality of corresponding resilient member 19 inaccordance with further ascent of the forging punch 20; wherein afterthe punch pieces are separated from the forged outer-ring 2 according tocontraction of the lower portions of the punch pieces, said methodfurther comprising the step of: ejecting the forge outer-ring outside ofthe lower die; wherein the head of the forging punch 20 formed by thepunch pieces and the slide member is formed of a continued surfacecorresponding to the spherical surface 5 and the ball track grooves 6 ofthe outer-ring 2 at the time of pressing the spherical inner surface 5Aof the pre-processed outer-ring 2A.